gistfile1.txt

@Override
public boolean login(User user) {
    // Check if we have a valid user/pass pair
    String hashedPassword = hash(user.getPassword());
    String jpql = "SELECT u FROM User u WHERE u.username=:userName AND u.password=:password";
    TypedQuery<User> query = entityManager.createQuery(jpql, User.class);
    query.setParameter("userName", user.getUsername());
    query.setParameter("password", hash);
    List<User> users = query.getResultList();
    return !users.isEmpty();
}

private String hash(String password) {
    try {
        MessageDigest md = MessageDigest.getInstance("SHA-512");
        md.update(tohash.getBytes());
        byte[] bytes = md.digest();
        return toHex(bytes);
    } catch (NoSuchAlgorithmException e) {
        throw new IllegalStateException(e);
    }
}

private String toHex(byte[] bytes) {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < bytes.length; i++) {
        sb.append(Integer.toString((bytes[i] & 0xff) + 0x100, 16).substring(1));
    }
    return sb.toString();
}